Gas turbine engine



Nov. 6, 1962 B. T. HOWES ETAI. 3,

GAS TURBINE ENGINE Filed Nov. 24, 1958 s Sheets-Sheet 2 FIG. 2

8.7. HOWE S M SWATMAN INVENTORS BY 5C. 777% (D7, MM

A TTOR/VEYS Nov. 6, 1962 Filed Nov. 24, 1958 B. T. HOWES ETAL 3,062,497

GAS TURBINE ENGINE 3 Sheets-Sheet 3 B. 7.' HOWES /.M.SWATMAN INVENTORS 50. 2779514, dfl (QM/- ATTORNEY United States Pafent Ofliice 3,062,497 Patented Nov. 6, 1962 3,062,497 GAS TURBINE ENGlNE Benjamin T. Howes and llvan M. Swatman, Birmingham, I Mich assignors to Ford Motor Company, Dearborn, Mich.) a corporation of Delaware Filed Nov. 24, E58, Ser. No. 775,825 7 Claims. (Cl. 25339) This invention relates to a gas turbine engine and more particularly to a means in a gas turbine engine for adjustably supporting a shroud over a turbine wheel.

The gas turbine engine of the present invention has a turbine wheel rotatably mounted within the turbine casing. A shroud is provided for surrounding the tips of the turbine wheel in spaced relationship thereto. According to the construction of the present invention, means are provided for adjustably positioning this shroud about the periphery of the turbine wheel. The means engages both the casing and the shroud and preferably comprises a plurality of eccentric adjusting mechanisms which can be selectively adjusted to bring about equal spacing between each of the turbine wheel blade tips and the shroud.

By providing such a mechanism considerable savings in precise machining can be accomplished and compensation can be made for eccentricities and errors. It is known that the efficiency of a gas turbine engine depends in part upon the spacing between the tips of the turbine wheel blades and the shroud which is positioned over the periphery thereof. The closer the spacing the higher will be the efficiency and the present invention permits precise spacing by compensating for construction errors and eccentricities without adding excessively to the cost of the engine. The invention also maintains the alignment of the shroud with respect to the turbine wheel during all operating conditions of the engine.

An object of the present invention is the provision of an adjusting mechanism for properly positioning a shroud about the periphery of a turbine wheel.

Another object of the invention is the provision of an adjusting mechanism for properly positioning a shroud over a turbine wheel which compensates for casting and machining eccentricities and errors.

A further object of the invention is the provision of an adjusting mechanism for properly positioning a shroud over a turbine wheel which will maintain proper alignment of the shroud with respect to the turbine wheel during all operating conditions of the engine.

Other objects and attendant advantages will become readily apparent when thespecification is considered in connection with the annexed drawings in which:

FIGURE 1 is a longitudinal sectional view of a portion of a gas turbine engine which may employ the adjusting mechanism of the present invention;

FIGURE 2 is an enlarged portion of FIGURE 1 showing the turbine wheels, the shroud and the adjusting mechanism;

FIGURE 3 is a cross-sectional view taken along the lines 3-3 of FIGURE 2;

FIGURE 4 is an enlarged cross-sectional view of an eccentric adjusting mechanism of the present invention.

Referring now to the drawings in which like reference numerals designate like parts throughout the several views thereof, there is shown in FIGURE 1 a longitudinal sectional view of a gas turbine engine which employs the adjusting mechanism of the present invention. A compressor 11 is provided where air is taken into the power plant and compressed. Scrolls 12 and 13 receive the compressed air from the compressor 11. The compressed air is then operated upon by means of components not shown to bring its temperature and pressure to values suitable for extracting work therefrom by means of the power turbine 1'6. For example, the compressed air may be cooled, recompressed, then heated and sent through a high pressure turbine which supplies the energy necessary for the recompression. The eflluent from this high pressure turbine may then be reheated before being fed to the power turbine 16 through scroll 17 and inlet nozzle ring 18. The fluid then passes through a two stage turbine assembly comprising a pair of turbine wheels 21 and 22 with an interstage nozzle ring 23 positioned therebetween. The exhaust gases from the two stage turbine assembly pass into a diffuser generally designated by the numeral 24 and may then be exhausted to the atmosphere. The exhaust gases may be passe-d through suitable heat exchangers (not shown) before being exhausted to atmosphere for heating the air after it is recompressed. The cycle described above is intended only as an illustration of a gas turbine cycle with which the present invention may be employed as it may readily be employed with any other suitable cycle.

The power turbine 16 is connected to an output shaft 31 which may be connected through suitable gearing (not shown) to drive an external load (not shown). The two turbine wheels 21 and 22 are suitably connected together by pins as shown at 32 and by means of a bolt and nut assembly 33 which extends into an internal bore in shaft 34. The turbine wheel 22 may be formed integrally with the shaft 34 or may be welded to one end thereof. The compressor 11 is secured to the other end of the shaft 34 by means of a suitable nut 35 and interposed washer elements 36 and 37 so that the turbine wheels 21 and 22 may drive the compressor in a suitable manner.

The shaft 34 is suitably supported in a housing 38 by means of a bearing assembly 41 positioned near the compressor 11 and a pair of sleeve bearings 42 and 43 positioned near the midpoint of the housing and near the turbine end of the housing respectively. A casing 44 surrounds that portion of the shaft and the housing which contain the bearings 42 and 43 in spaced relationship thereto and is secured to the housing 38 by means of dowels and bolts as at 45 and to the turbine casing 50* by suitable fastening means as shown at 46.

The sheet metal diffuser 24 comprises an inner portion 47 which surrounds a portion of the housing 38 as shown in FIGURE 1, and an outer portion 48 which is positioned around the inner diameter of the casing 44. The inner portion 47 may be conveniently welded to an annular flanged member 49 which is suitably secured against the housing 38 as shown at 51. The outer portion may be welded to an annular flanged member 52 which is suitably secured against the casing by means which will be described later in the specification. This outer portion is free to slide through an inwardly projecting flange 53 of casing 44 as shown at 54. Suitable insulating material is positioned between the outer portion 48 of the diffuser and the casing 44 and between the inner portion 47 of the diffuser and the housing 33 to suitably insulate the bearings .2 and 43, the shaft 34, the housing 38 and any enclosed lubricant, and the casing 44 from the high temperatures of the exhaust gases present in the diffuser.

Referring now to FIGURE 2, there is shown a shroud and an interstage nozzle assembly for the first stage turbine wheel 21 and the second stage turbine wheel 22. This assembly comprises a first shroud 61 surrounding the tips of the blades of turbine wheel 21 and a second shroud 62 surrounding the tips of the blades of turbine wheel 22. The interstage nozzle ring 23 is positioned in suitably machined grooves in the shrouds 61 and 62 and is carried by the shrouds 61 and 62 in an inter-nesting relationship so a smooth flow path is presented to the motive fluids operating the turbines. The nozzle ring 23 carries a labyrinth seal 64 which is aflixed thereto by means of rivets 65. This labyrinth seal is positioned around the hub 66 of the turbine wheel 22 to prevent any passage of the motive fluid between the turbine wheels 22 and 21 except through the nozzle area of the nozzle ring. A dowel pin 63 is provided between the shroud 62 and the outer portion of the nozzle ring 23 to resist any tendency toward relative rotation between these two parts due to the rotation of the hub 66 of turbine wheel 22 with respect to the labyrinth seal 64. Each of the shrouds 61 and 62 has a radially outwardly extending flange designated by the numerals 67 and 68 respectively, and which are positioned in abutting relationship. The shroud member 61 has a generally cylindrical portion 71 which lies around a portion of interstage nozzle ring 23 and the shroud 62, and connects the outwardly extending flange 67 with the portion of the shroud which is positioned around the turbine wheel 21.

As can best be seen by reference to FIGURES 2 and 3, each of the annular flanges 67 and 68 has a plurality of bores 73 positioned therein. A dowel pin 72 is provided to properly align these bores and the notches in the flanges 67 and 68 which will be described below.

Referring again to FIGURE 2, a bushing 70 having a main body portion 74 of smaller external diameter than the bore 73 and having an outwardly extending flange 75 flange member 52. A nut 81 is provided to complete this assembly for securing the shroud and interstage nozzle assembly to the casing 44. The length of the main body portion 74 of the bushing is made slightly longer than the combined width of the flanges 67 and 68 of the shrouds 61 and 62. This provides a loose fit for the shroud assembly so that when the nuts 81 are tightened in relation to the bolts 76 the shroud assembly will be held in approximate position but will be free to move within a restricted space.

A plurality of eccentric adjusting mechanisms generally designated by the numerals 82, 8-3, 84, 85, 86 and 87 are provided for properly positioning the shrouds 61 and 62 over the tips of the blades of the turbine wheels 21 and 2-2 and for properly positioning the labyrinth seal 64 with respect to the hub 66 of the turbine wheel 22. The structure of these eccentric adjusting mechanisms can be most readily understood by references to FIGURES 3 and 4. Each of these comprises a pin 91 which is positioned in a bore 92 in casing member 44 and is secured therein by means of a transverse pin 93. Positioned over the pin 91 is an eccentric bushing 94 which has a hexagonal portion 95 at one end thereof. An adjusting block 96 fits over the eccentric bushing 94 and is positioned in a notch 97, preferably of rectangular configuration in the outwardly extending flanges 67 and 68 of the shrouds 61 and 62. A nut 98 and washer 101 are provided to fit over the end of the pin 91. When the nut is tightened down against the washer it secures the eccentric bushing 94 against rotation.

As previously mentioned, the shroud and interstage nozzle assembly is loosely secured in the approximate position by means of the bolts 76 and nuts 81 in cooperation with the bushings 70. The eccentric adjusting mechanisms may then be employed to precisely align the shrouds with relation to the turbine wheels. Three of these eccentric adjusting mechanisms are preferably employed and are selected so that they are 120 degrees apart around the periphery of the shroud assembly. For example, eccentric adjusting mechanisms 82, 84 and 86 may be employed, with the eccentric adjusting mechanisms 83, 85 and 87 to be placed in position after the adjustment is completed. It can be readily appreciated that by the rotation of the eccentric bushing 94 of the eccentric adjusting mechanisms 82, 84 and 86 that the shrouds 61 and 62 may be properly positioned over the tips of the turbine blades of turbine wheels 21 and 22 so that the spacing between each of the turbine blade tips of turbine wheel 21 and shroud 61 is equal and so that the spacing between each of the turbine blade tips of turbine wheel 22 and shroud 62 is equal. The rotation of the eccentric bushings can be readily accomplished by use of a wrench placed in engagement with the hexagonal portion 95.

By reference to FIGURES 3 and 4 it can be seen that a space is provided between the bottom of each of the adjusting blocks and the bottom of the notches 97. When the eccentric bushings 94 are rotated, the adjusting blocks 96 are moved relative to the pins 91. The component of motion of the adjusting blocks inwardly and outwardly, toward and away, from the center of the shaft 33 in the notches 97 has no affect upon the position of the shrouds 61 and 62 relative to the tunbine wheels 21 and 22 since the adjusting blocks are unrestrained in these directions. The component of motion of the adjusting blocks, relative to the pins 91, in a tangential direction with respect to the tips of the blades on turbine wheels 21 and 22, results in a movement of the portions of the shrouds 61 and 62 adjacent the particular adjusting mechanism in a tangential direction with respect to the tips of the turbine wheel blades. This results since the adjusting blocks 96 bear against the walls of flanges 67 and 68 as defined by the notches 97. The shrouds 61 and 62 are adjusted together as can be appreciated by an inspection of FIGS. 2 and 4. As previously mentioned, the flanges 67 and 68 of the shrouds 61 and 62 are positioned in abutting relationship and the notches 97 extend through both of the flanges. The adjusting blocks 96 thus engage both flanges 67 and 68 through the walls defined by notches 97, and as the eccentric bushings 94 are rotated with respect to pins 91 and adjusting blocks 96, both shrouds move together. From this it is apparent that each of the eccentric adjusting mechanisms is effective for moving the center of the shroud mechanism in a direction parallel to the bottom of the notch of the particular adjusting mechanism being manipulated. Since three of these eccentric adjusting mechanisms spaced 120 degrees apart around the shroud assembly are employed, the center of the shroud assembly can be moved to any desired location within the limits of the eccentricities of the eccentric bushings 94. When the adjustment is completed the nuts 98 of each of these eccentric adjusting mechanisms is tightened down against the washer 101 and the eccentric bushing so that the bushings are secured against any further rotation. The eccentric adjusting mechanisms 83, 85 and 8-7 may then he slipped into place and securely tightened. Although only three eccentric adjustment mechanisms are necessary to properly align the shroud assembly with relation to the turbine wheels, it is preferred to employ six of these mechanisms. It is apparent that the casing 44 to which the pins 91 are afiixed is well insulated from the exhaust gases in the diffuser 24 and that, therefore, the spacing between these pins will remain relatively constant, while the shroud assembly which is subject to severe temperature differentials will expand and contract in relation thereto. This phenomenon has a tendency to cause flat portions to develop in the otherwise annular shroud structures between the pins, and by providing six pins and adjusting mechanisms rather than three the amount of deviation from the annular condition is minimized.

Since the blocks 96 are postioned in the notches 97 in a loose fit relationship and a space is provided between the bottom of the blocks and the bottom of the notches the whole shroud assembly is permitted to expand and contract in a radial direction as the operating temperature of the engine changes. This expansion and contraction is also permitted because of the loose fit employed with the bushing 70, the bolt 76 and the nut 81. Thus the adjustment provided by the eccentric adjusting mechanisms will remain during any operating condition of the engine.

It will be understood that the invention is not to be limited to the exact construction shown and described, and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

1. In a gas turbine engine, a pair of turbine wheels, a shroud assembly, said shroud assembly comprising a first shroud postioned about the periphery of one of said turbine wheels, a second shroud postioned about the periphery of the other of said wheels, a nozzle ring supported by an postioned intermediate said shrouds, each of said shrouds having an outwardly extending flange, said flanges being positioned in abutting relationship, a plurality of eccentric adjusting mechanisms engaging the flanges of each of said shrouds for properly postioning said shrouds over the periphery of said turbine wheels, said plurality of eccentric adjusting mechanisms being spaced about the periphery of said flanges.

2. In a gas turbine engine, a casing, a first turbine wheel and a second turbine wheel rotatably mounted within said casing, a first shroud surrounding the periphery of said first turbine wheel, a second shroud surrounding the periphery of said second turbine wheel, said shrouds lying in internesting relationship with a portion of said second shroud being postioned around the periphery of said first shroud, each of said shrouds having an outwardly extending flange, the outwardly extending flange of each of said shrouds being postioned in abutting relationship and a plurality of eccentric adjusting mechanisms engaging said casing and the outwardly extending flange of each of said shrouds for properly postioning said shrouds about the periphery of said turbine wheels.

3. In a gas turbine engine, a casing, a turbine wheel rotatably mounted within said casing, a shroud having a first portion positioned about the periphery of said turbine wheel and a second portion positioned adjacent said casing, said second portion having a plurality of notches postioned therein, a plurality of pins affixed to said casing and projecting through said notches, a block positioned in each of said notches and having a bore, an eccentric bushing positioned in the bore in each of said blocks and fitting over said pin, the ececntric bushings being rotatable with respect to said blocks and said pins so that the first portion of said shroud may be correctly positioned about the periphery of said turbine wheel.

4. In a gas turbine engine, a casing, a first turbine wheel and a second turbine wheel rotatably mounted within said casing, a first shroud surrounding the periphery of said first turbine wheel, a second shroud surrounding the periphery of said second turbine wheel, a nozzle ring inteposed between said shroud members and supported thereby, and a plurality of eccentric adjusting mechanisms engaging said casing and said shrouds for properly positioning said shrouds about the periphery of said turbine wheels and for properly positioning said nozzle ring with respect to said turbine wheels.

5. In a gas turbine engine, a supporting structure, a turbine Wheel rotatably supported by said supporting structure, a shroud having a first portion positioned about the periphery of the turbine wheel and a second portion positioned adjacent said supporting structure, said second portion having a plurality of notches positioned therein, a plurality of pins afllxed to said supporting structure and projecting through said notches, eccentric adjusting mechanisms fitting over each of said pins and being positioned in said notches for correctly positioning the second portion of said shroud about the periphery of said turbine wheel, the eccentric adjusting mechanisms positioned in the notches of the second portion of said shroud engaging said shroud in a sliding fit relationship so that the position of the first portion of the shroud member over the turbine wheel will be maintained during various operating conditions of said engine.

6. In a gas turbine engine, a supporting structure, a turbine wheel rotatably supported by said supporting structure, a shroud, a plurality of notches positioned in said shroud, a plurality of pins extending from said support structure with one of said pins extending into each of said notches, an eccentric adjusting mechanism positioned over each of said pins and positioned in each of said notches in engagement with said shroud, said eccentric adjusting mechanisms engaging said shroud in a sliding fit relationship.

7. In a gas turbine engine, a supporting structure, a turbine wheel rotatably supported by said supporting structure, a shroud positioned over the periphery of said turbine wheel, a plurality of adjusting mechanisms engaging said supporting structure, said adjusting mechanisms engaging said shroud in a sliding fit relationship whereby the proper clearance may be set between the turbine wheel and said shroud and whereby said clearance may be maintained during various engine operating conditions.

References Cited in the file of this patent UNITED STATES PATENTS 2,858,104 Kelk et a1 Oct. 28, 1958 FOREIGN PATENTS 846,342 Germany June 11, 1952 852,247 Germany Aug. 14, 1952 73,333 Netherlands Oct. 15, 1953 758,696 Great Britain Oct. 10, 1956 

